Beta-thiolactones



United States Patent 3,520,903 BETA-THIOLACTONES Arleen C. Pierce,Monmouth Junction, N.J., asslgnor to Allied Chemical Corporation, NewYork, N.Y., a corporation of New York No Drawing. Filed Oct. 6, 1967,Ser. No. 673,259 Int. Cl. C07d 61/00 U.S. Cl. 260-327 7 Claims ABSTRACTOF THE DISCLOSURE This specification discloses a process for thepreparation of fi-thiolactones whereby carbonyl sulfide is reacted withan ethylenically unsaturated compound in the presence of actinicradiation having a wave length between 2800 and 366 angstrom units. Thisprocess can be used to prepare known ,B-thiolactones and novelperhalogenated B-thiolactones which are useful as monomers for thepreparation of polyesters as well as chemical intermediates for thepreparation of thiocarboxylic acids or their ester and amidederivatives.

Several processes are known for the preparation of ,8- thiolactones, butnone are completely satisfactory. In US. Pat. 2,978,460, there isdisclosed a process for the preparation of betaand gamma-thiolactones byreaction of the corresponding betaand gamma-halo acid halides with ametal sulfide containing a controlled degree of hydration undersubstantially anhydrous conditions. In practice, however, it isdifiicult to obtain the metal sulfide in sufficiently pure anhydrousstate and to maintain anhydrous conditions during the reaction. M.Linkova et al., Isvest. Akad. Nauk, SSSR, Otdel, Khim. Nauk, pp. 569-570(1955), describe a process for the preparation ofB,fl'-dimethylpropiothiolactone whereby the triethylammonium salt ofmercaptoisovaleric acid is reacted with chloroformic acid at C.Knunyants et al., Isvest. Akad. Nauk, SSSR, Seriya Khim., No. 4, pp.644651 (1964), describe a process for the preparation of fl-thiolactonessubstituted in the alpha-position by reacting the corresponding 5-halo-acid chloride in dilute solution with hydrogen sulfide in thepresence of triethylamine. These processes are specific for a limitedclass of products, and unsubstituted B-thiolactones cannot be preparedby these methods.

It has now been discovered that B-thiolactone compounds may be readilyprepared by reacting carbonyl sulfide with an ethylenically unsaturatedcompound in the presence of actinic light. The process of the presentinvention possesses the advantages of utilizing readily available,inexpensive starting materials and is generally applicable topreparation of a wide variety of fl-thiolactone products. In addition toknown fi-thiolactones, certain novel perhalogenated B-thiolactonecompounds may be prepared by the present process.

In accordance with one aspect of the present invention, fl-thiolactonecompounds conforming to the general formula:

wherein each R individually represents a member selected from the groupconsisting of hydrogen, halogen having an atomic weight below about35.5, alkyl, haloalkyl wherein each halogen subsituent has an atomicweight below about 35.5, aryland alkyl-, haloand haloalkyl-substitutedderivatives thereof wherein each halogen substituent has an atomicWeight below about 35.5 are prepared by reacting,

in the presence of actinic radiation of wave length of about 2800 to3600 angstrom units, carbonyl sulfide with a liquid ethylenicallyunsaturated compound having the formula:

wherein each R has the above defined meaning, with the proviso that notmore than an alkyl, haloalkyl, aryl or substituted aryl group is presenton any one ethylenically unsaturated carbon atom.

Another aspect of the present invention is the provision of fullyhalogenated B-propiothiolactone compounds which are believed to be newchemical compounds. These perhalogenated fl-propiothiolactone compoundsmay be represented by Formula I, above, wherein each R individuallyrepresents halogen having an atomic Weight below about 35.5 or aperhaloalkyl group having from 1 to 12, preferably 1 to 8, carbon atoms,in which all halogen atoms have an atomic weight below about 35.5

Referring to Formula II, above, wherein one or both carbon atoms of theethylenically unsaturated compound are substituted by alkyl, haloalkyl,aryl or substituted aryl substituents, it is desirable that not morethan one such substituent be present on any one ethylenicallyunsaturated carbon atom since such bulky radicals, due to sterichindrance, tend to seriously impair the reaction rate. When theethylenically unsaturated compound is substituted by alkyl, haloalkyl,aryl or substituted aryl groups, the number of carbon atoms containedtherein is not critical provided that the ethylenically unsaturatedcompound is in the liquid state under the reaction conditions. Ingeneral, however, when R represents an alkyl or haloalkyl radical, thenumber of carbon atoms contained threin may range from 1 to about 18,although alkyl or haloalkyl substituents containing from 1 to 8 carbonatoms are preferred. When R represents an alkylor haloalkyl-substitutedaryl group, the alkyl or haloalkyl substituent will normally containfrom about 1 to 4 carbon atoms. Typical aryl substituents includephenyl, naphthyl, and the like. Ethylenically unsaturated compoundshaving from 1 to 8 carbon atoms and containing only carbon, hydrogen andhalogen atoms constitute preferred embodiments of ethylenicallyunsaturated compounds suitable as starting materials in the process ofthe present invention.

Representative specific ethylenically unsaturated compounds that may beemployed as starting materials in the process of the present inventioninclude ethylene; propylene; butene-l; butene-Z; isobutylene; pentene-l;pentene-Z; 2-methylbutene-1; 3-methylbutene-l; hexene-l; heptene-l;octene-l; 1,1-dichloro-2,2-difiuoroethylene; 1, 1difluoro-2-chloro-2-fluoroethylene; 1 chloro-l-fluoro-2-chloro-2fluoroethylene; 1 fluoro-1-chloro-2-dichloroethylene;tetrafluoroethylene; vinylidene fluoride; l-chloro-2,2-difiuoroethylene;l-chloro 2 chloro-2-fluoroethylene; 1-fluoro 2,Z-dichloroethylene;l-fluoro-l-chloroethylene; 1 fluoro-Z-chloroethylene;1,1-difluoro-2-fluoro-3- chloro-3,3-difiuoropropene l;1,1-difiuor0-2-fluoro-3,3,3- trifluoropropene-l;1,1-difluoro-2-fluoropropene 1; 1,1,1- trifluoro-2-fluoro-3-chloro-4,4,4trifluorobutene 2; 1,1- difiuoro 2 fiuoro 3 fiuoro-3-chloro-4-chloro-4,4trifiuorobutene-l; 2-fiuoro-3,3-difiuoro-4,4,4-trifluorobutene 1;2-fiuorobutene-1; styrene; stilbene; allylbenzene; 4- methylstyrene; 4chlorostyrene; 4 fluorostyrene; 3 trifluoromethylstyrene;3-chloromethylallybenzene; and the like. If desired, mixtures ofethylenically unsaturated compounds may also be employed as startingmaterials in the process in which case the corresponding mixtures offlpropiothiolactones will be obtained as products.

3 The reaction which occurs in practice of the present invention may berepresented by the following equation in which each R has the abovedefined meaning:

The reactant proportions may be varied over a wide range, for example,from about one mol to about five mols, and higher, of carbonyl sulfideper mol of ethylenically unsaturated compound. In general, it isdesirable to employ a stoichiometric excess of carbonyl sulfide in orderto effect maximum conversion of the ethylenically unsaturated compoundto desired ,B-propiothiolactone. Accordingly, preferred reactantproportions range from about 1.1 to about 2 mols of carbonyl sulfide permol of ethylenical- 1y unsaturated compound.

As previously indicated, the reaction is conducted in the presence of alight source of sufiicient radiation to catalyze the reaction betweenthe ethylenically unsaturated compound and carbonyl sulfide. It has beenfound that the light source which is capable of catalyzing the reactionmust have an actinic radiation wave length of about 2800 to about 3600Angstrom units and more advantageous results are obtained when theradiation wave length is maintained during the radiation between about3000 to 3200 Angstrom units. Actinic radiation of the required wavelength is readily obtainable from any conventional light source such ashigh or low pressure mercury vapor lamps, and ultra-violet fluorescentlight. The light source may be used alone or in conjunction with wellknown photosensitizers such as acetone, acetophenone and benzophenone,which may be present in an amount generally ranging from about 0.5% to5% by weight, based on the weight of the reaction mixture.

It is additionally essential that the reaction be carried out at suchtemperatures as to maintain the ethylenically unsaturated compound inthe liquid state. At reaction temperatures above the boiling point ofthe ethylenically unsaturated compound, the reaction, which is highlyexothermic, may become uncontrollable. At very low temperatures,however, the formation of episulfides and their polymers becomes thepredominant reaction which materially lowers the yield of desiredB-propiothiolactone product. Accordingly, suitable temperatures at whichthe reaction may be conducted at atmospheric pressure map range fromabout 80" C. to about 35 0, although temperatures in the range fromabout C. to 50 C. are preferred.

The reaction is conducted for a time sufficient to permit formation ofat least some fi-propiothiolactone product. In general, the reaction isdependent upon several factors, such as the reactivity of theethylenically unsaturated reactant, temperature, and the like, and isvaried from about 1 hour up to about 20 hours. Normally, a longerreaction time will result in increased yields of the desiredfipropiothiolactone product.

Although the reaction will proceed in the absence of any diluent, ifdesired, an organic liquid which is inert to the ethylenicallyunsaturated compound and carbonyl sulfide reactants and to theB-propiothiolactone product and which will remain liquid at thetemperatures of the reaction may be employed as diluent and/0r solventtherefor. In those cases where the reaction is particularly exothermic,the presence of an inert diluent will aid in dissipating the heat ofreaction. Suitable organic liquids which may serve as diluents in thereaction include aliphatic and cycloaliphatic hydrocarbons such asethane, n-propane, n-hexane, n-heptane, n-octane, cyclohexane, and thelike.

Although the presence of water does not render the process inoperative,it is preferred that the reation be carried out under anhydrousconditions since there is a possibility that the fi-propiothiolactoneproduct may be hydrolyzed if sufiicient water is present. The order ofaddition of the reactants is not critical, and thus, the carbonylsulfide, either in liquid or gaseous form, may be added to the liquidethylenically unsaturated compound, either alone or in solution. Theorder of addition may be reversed if desired by adding the liquidethylenically unsaturated compound to the carbonyl sulfide reactant.Alternatively, the ethylenically unsaturated compound and carbonylsulfide reactants may be fed simultaneously into the reactor eitherundiluted or with a diluent. The preferred method is to charge theethylenically unsaturated compound, alone or with a diluent and/or aphotosensitizer, into a reactor, purge the reactor with a stream ofpurified nitrogen, introduce into the reactor the desired quantity ofcarbonyl sulfide either alone or with a diluent, and subject the reactorcontents to irradiation for the desired reaction time.

The fi-propiothiolactone product may be separated from the reactionmixture by conventional methods, such as by fractional distillation toremove unreacted ethylenically unsaturated compound and carbonylsulfide, low boiling by-products and, if employed, organic diluent, andis recovered as the distilland. Alternatively, the ,B-propiothiolactonemay be recovered by crystallization from a concentrated solution if itis a solid at room temperature.

The following examples illustrate practice of the invention but are notconstrued as being limiting on the same. The reactor employed was aquartz lined reactor fitted with a Hanovia 450-watt high-pressure quartzmercury vapor lamp enveloped by a Pyrex filter, inlet tube for gases,reflux condenser, and stirrer.

EXAMPLE 1 A reactor of the type described above was purged with a streamof nitrogen which had been previously purified and dried by passingcommercially available nitrogen through a mixture containing about 1.25mols pyridine, 0.01 mol triphenylmethane and 0.01 mol lithium aluminumhydride. To the purified reactor there was first added 3 m1. of acetoneand then there was condensed, at a temperature of 72 C., 2.0 mols ofcarbonyl sulfide and 0.53 mol of 1,1-dichloro-2,2-difluoroethylene. Theresultant mixture, While being maintained at about said temperature, wasthen subjected to actinic radiation of wave length of about 2900-3300Angstrom units over a 21 hour period. Unreacted carbonyl sulfide,1,1-dichloro-2,2-difluoroethylene and other volatile materials wereremoved by warming the reactor to room temperature. The liquid product,as determined by gas-liquid chromatography, showed a yield of 57% ofoc,a-diChlOXO- fl,B-difiuorofi-propiothiolactone and 1.7% ofa,a-difiuorofl,,B-dichlorofi-propiothiolactone.

The fi-propiothiolactone structure of the resultant products wasconfirmed by infrared analysis which showed a 1/ max. C=O of 1730 cm.-for a,a-dichloro-B,B-difiuorofl-propiothiolactone and a 11 max. C=O of1750 cm.- for the a,a-difluoro-/3-,B-dichloro-/3-propiothiolactone.

EXAMPLE 2 A reactor of the type described above was purged with nitrogenprepurified in the manner described in Example 1. To the purifiedreactor there was first added 3 ml. of acetone and then there wascondensed, at a temperature of 72 C., 1.66 mols of carbonyl sulfide and1.71 mols of 1,1difluoro-Z-chloro2-fluoroethylene. The resultantmixture; while being maintained at about said temperature, was thensubjected to actinic radiation of wave length of about 29003300 Angstromunits over a 10-hour period. Unreacted carbonyl sulfide, 1,1-difiuoro-2-chloro-2-fluoroethylene and other volatile materials were removed bywarming the reactor to room temperature. The liquid product, asdetermined by gas-liquid chromatography, showed a yield of 63.7%a-chloroa,[Lfl-trifluoro-B-propiothiolactone and 4.5% of,B-chloroct,0t,fi-tIlflllOIO-B-PIOPlOthlOlZiCtOllfi.

The B-propiothiolactone structure of the resultantachloro-a,,8,,B-trifiuoro-B-propiothiolactone product was confirmed byinfrared analysis which showed a 1 max. C=O of 1730 cmr EXAMPLE 3 Into areactor of the type described above there was charged 2.5 mols of driedtechnical grade pentene (a commercially available mixture of n-pentene-land npentene-2) The reactor was purged with a stream of nitrogenprepurified in the manner described in Example 1, above, andbenzophenone in an amount of approximately 0.1% by weight of the reactorcontents was added to the reactor. 2.83 mols of carbonyl sulfide werethen bubbled into the reactor over a period of about 50 minutes. Theresultant mixture was then subjected to actinic radiation of wave lengthof about 2900-3300 Angstrom units over a l-hour period while maintainingthe temperature of the reactor contents in the range of about 2l36 C.Unreacted carbonyl sulfide, pentenes and other volatile materials wereremoved by fractional distillation and a liquid product comprised of amixture of a-n-propyl-B-propiothiolactone, fl-n-propyl-fipropiothiolactone, a-ethyl-B-methyl-B-propiothiolactone anda-methyl-jS-ethyl-fl-propiothiolactone was recovered as distilland. Thetotal yield of B-propiothiolactone product was 16% by weight ascalculated by gas-liquid chromatography. The B-propiothiolactonestructure of the product was confirmed by infrared analysis which showeda 11 max. C=O of 1740 cm.-

The B-propiothiolactones prepared by the process of the presentinvention are useful for many purposes. For example, thefl-propiothiolactones may be reacted chemically with bone dry cottonlinters to add sulfur-containing side chains to cotton fibers. Thefi-propiothiolactones may also be polymerized in the presence of a freeradical catalyst by known procedures to polyesters having a wide rangeof utility. For example, the relatively low molecular weight polyestersare useful in preparation of plasticizers, cosmetics, polishes and waxesand can also be used as thickening agents for various lubricants. Thehigher molecular weight polyesters are useful in the preparation ofmolded articles, films, fibers and the like. The B-propiothiolactoneproducts of the present invention will also undergo base-catalyzedaddition reactions with such nucleophilic compounds as sodium hydroxide,sodium methoxide, sodamide, primary and secondary amines, and the like,to prepare the corresponding thiocarboxylic acids, esters, amides, etc.which exhibit a variety of uses themselves or may serve as intermediatesfor the preparation of other useful compounds. For example, thethiocarboxylic acids may be employed as antioxidants for organichydrocarbons, as color stabilizers, and catalysts for phenol ketonecondensation reactions.

Since various changes and modifications may be made in the inventionwithout departing from the spirit thereof it is intended that all mattercontained in the above description be interpreted as illustrative andnot in a limiting sense.

I claim:

1. A perhalogenated ,B-propiothiolactone compound having the formula:

References Cited Knunyants et al.: C. A. 61, 2966, Aug. 3, 1964.

HENRY R. JILES, Primary Examiner C. M. SHURKO, Assistant Examiner US.Cl. X.R.

3 3 UNITED sTXTEs PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,520,903 Dated July 21, 1970 Inventor(s) Arleen C. Piege It iscertified that error appears in the shove-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Colunm 1, line 16 "366" should be 3600-.

Colunm 1, line 62 "R- C- C==S" should be R-C C= =O Column 1, line 68"subsituent" should be substituent--.

Column 2, line ll "an" should be -one-.

Column 3, line 49 "map" should be -ma.y--.

Column 3, line 73 "reation" should be reaction---.

Claim 1, line 29 "haloalkyl" should be --halomethyl--.

Claim 2, line 33 "haloalkyl" should be --halomethyl.

olifi'iiifrui SEALEU m'rzom Attest:

mm 1:. m.

Offic Gamissioner of Patents

